This invention relates to the field of rotary machines and more particularly to the field of rotary compressors and continuous combustion rotary engines.
Combustion engines use pressurized working fluid, such as expansion gases and/or combustion gases, to impart rotating motion to a shaft. In the case of a reciprocating piston driven engine, combustion gases explode to drive a piston thereby causing rotation of a crankshaft. For a gas turbine engine (Brayton Cycle Engine), pressurized combustion gases that are provided to blades connected to a shaft cause the shaft to rotate. Similarly, for a steam turbine engine (Rankine Cycle Engine), a shaft is rotated by providing pressurized steam to blades connected to the shaft.
A drawback to the reciprocating piston engine is that the sudden and extreme force placed on the pistons by the expanding combustion gases (nominally 400 to 600 p.s.i. at 2000 r. p.m.) tends to cause fatigue in the moving parts. Furthermore, the intermittent burning of fuel in the cylinders is relatively inefficient compared to burning fuel continuously and incomplete burning is a primary cause of pollutants. Also, much of the energy in a piston engine is radiated as heat and hence lost.
A turbine rotary engine (Rankine or Brayton cycle) overcomes the problem of sudden and extreme force associated with reciprocating piston engines by providing to the blades a continuous stream of working fluid at a relatively constant pressure. However, turbine engines are subject to a phenomena called "blade slip" wherein working fluid passes over and past the blade without doing any physical work. In order to minimize blade slip, turbine engines are operated with relatively high fluid pressures, thereby limiting the adjustability of the operating range of the turbine engines. For example, for some steam turbine engines, effecting a speed adjustment can take as long as an hour and a half.
Sliding vane machines have blades attached to a hub and arranged perpendicular to the direction of rotation. The blades rotate inside a non-circular housing. The blades are capable of expanding and contracting longitudinally so that compartments formed by pairs of blades, the hub, and the interior surface of the housing have a variable volume, thereby allowing for compression and expansion of the working fluid. This arrangement addresses the sudden and uneven combustion problems of piston engines and overcomes the "blade-slip" problem associated with turbine engines.
However, the amount of work that can be performed by the working fluid varies according to the compression ratio (i.e. the ratio of greatest to smallest compartment volume) which, for a sliding vane turbine, is relatively low and usually does not exceed approximately three to one.
An object of the present invention is to overcome the above-mentioned problems and to provide compact energy efficient rotary machines and engine systems utilizing same.
According to preferred embodiments of the present invention, a rotary machine is provided which includes an outer housing having a predetermined curvilinear interior surface with an outer housing central axis associated therewith. A rotatable outer hub assembly is disposed inside the outer housing and has an outer hub assembly central axis associated therewith located at a distance from the outer housing central axis. An inner rotatable hub is disposed inside the outer hub assembly and has an inner hub central axis associated therewith which is substantially coaxial with the outer housing central axis. A plurality of blades are hingedly connected at one end to the inner hub and radiate through the outer hub assembly to contact the interior surface of the outer housing at the other end of the blades. Thus a plurality of relatively airtight compartments are formed between the interior surface of the outer housing, the outer hub, and respective pairs of the blades. During operation, the volume of the compartments varies according to the rotational angle of the respective pairs of blades.
Due to the fixing of the radial inner ends of the blades at the inner hub and the offset of the axes of the inner hub and outer hub assembly, the blades are precisely controlled to progressively change their angular orientation and therewith the size of the compartment volumes for each rotational cycle of operation. The interior surface of the outer housing is configured to match the location of the blade outer tips as both the inner and outer hubs are rotated. Thus, the blades need not and do not slide or expand radially, but rather, are precisely positively controlled by their connection to the inner hub and their sliding engagement at the outer hub.
In operation, the rotary machine transfers forces between the blades and the inner hub by way of the outer hub assembly forming effective abutments for the blades acting as levers. When the rotary machine is operated as part of an engine, motive pressurized fluid acts on the blades to cause them to move and push the outer hub assembly which is drivingly connected to rotate together with the inner hub. The angular orientation of the blades from radial is constantly changed in dependance on the rotative position of the outer hub assembly due to the offset at the outer hub assembly with respect to the inner hub and the effective "sliding" fulcrum at the locations where the blades radially extend through the outer hub assembly. Coupled with this angular change in the blades are changes in the effective pressure area of the blades and in the volumes between the blades discussed in more detail elsewhere herein.
When the rotary machine is operated as a compressor, the inner hub is rotated, which drivingly rotates the outer hub assembly, causing the blades to operate to compress fluid supplied thereto.
When serving as part of an engine, the rotary machine has an inlet for receiving working fluid and an exhaust for venting working fluid. The incoming working fluid is pressurized and acts on the blades to move the blades, which are drivingly engageable with the outer hub assembly. A drive transmission connects the outer hub assembly and inner hub such that the inner hub, and an output shaft connected thereto, is rotatably driven. In especially preferred embodiments, the inner hub and outer hub assembly rotate at the same rotational velocity. A combustor is provided for burning gases in a combustion chamber which are provided as working fluid to the inlet of the rotary machine. In a preferred machine embodiment, a compressor is provided for providing compressed air to the combustor. The combustor also heats an expansion gas which is mixed with the burning gas before being provided in the inlet.
In a preferred embodiment of the invention, the compressor is constructed as a second rotary machine which is substantially similar to the first rotary machine and is connected by a common drive shaft.
In certain preferred embodiments, the rotary machine has grooves cut into the interior surface of the outer housing for allowing working fluid in one compartment to pass through to another adjacent compartment.
In especially preferred embodiments of the present invention, the rotary machine is operated by providing to the inlet an expanding working fluid containing a predetermined amount of a combusted gas and a predetermined amount of an expansion gas. The amounts can also be varied during operation. Also, oxygen can be added to the combustion gas during combustion according to contemplated preferred embodiments.
Advantages of the present invention include increased fuel efficiency, reduction of emissions of pollutants, simple design, light weight, and small size. The invention can advantageously be operated closed cycle, open cycle, or a combination thereof. The invention can simultaneously utilize two types of working fluid: combustible gases and expansion gases. The amount of each can be varied during operation depending upon the availability of each and the load placed on the rotary machine system. Furthermore, the rotary machine of the present invention is advantageously adaptable to continuous combustion which provides for less noise than explosive, piston-driven engines and less wear on moving parts. Also, equalization of forces on the blades results in decreased eccentric loading on the moving parts.
Certain preferred rotary machine engine arrangements of the present invention are especially fuel efficient because heat produced by combustion, which would otherwise be radiated and lost, is used to heat an expanding working fluid, such as steam. The substantial compression ratio obtainable according to preferred embodiments of the invention allows for substantial work to be performed by the expansion gases. Since the compartments between the blades are relatively airtight, the problem of blade slip, which is usually associated with rotary turbine engines, is eliminated.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.